It is well known that conventional phone systems assign a phone number to each phone device in a phone network. To place a call to a target phone device, one dials the phone number assigned to the target phone device. The phone service provider receives the call request and initiates a call alert in the phone network to the target phone device.
During the call alert, the target phone typically rings to indicate occurrence of an incoming call. If the target phone device goes unanswered, the calling party may end the attempt to reach the target phone device or the caller alert period may time out. If the user of the target phone device accepts the incoming call (i.e., answers the phone), a two-way communication link is established between the calling party and target phone device.
Most phone numbers are publicly available to telemarketers unless the subscriber requests the phone number to be unlisted. Telemarketers typically make calls to publicly available phone numbers to sell products and/or services. In most instances, telemarketer calls are annoying to recipients. Unfortunately, if a phone number is registered as unlisted, friends of the subscriber cannot easily obtain the phone number of the subscriber. Thus, there is a tradeoff between making a phone number publicly available (potentially inviting telemarketing calls) and registering the phone number as being unlisted (preventing legitimate persons from obtaining a phone number).
Because receiving calls from telemarketers is so annoying, attempts have been made to reduce the amount of unwanted telemarketer calls to phone subscribers. For example, the government has set up a so-called Do Not Call (DNC) list. One can register their phone number on the Do Not Call list to provide notification that a subscriber assigned the phone number does not wish to receiving telemarketing calls to the registered phone number. In theory, the telemarketers should not make calls to the phone numbers on the Do Not Call list. However, in reality, the telemarketers often call without regard to the wishes of the receiving parties not to receive unsolicited phone calls. This is particularly disturbing because the DNC list does not serve the intended purposes of reducing or eliminating telemarketing calls.